1. Field of the Invention
The present invention relates to a seal device disposed between a pair of relatively rotating elements typically seen in the rollers of a crawler, track roller, reduction gear, hydraulic motor or the like. More particularly, the invention relates to a seal device in the reduction gear unit of automobiles or hydraulic motors of a variety of machinery, which provides an effective seal at the interface of relatively moving elements against a process fluid containing slurry or a high pressure process fluid.
2. Description of the Related Art
Primary related art of the present invention is found as a seal ring in U.S. Pat. No. 6,086,069. A similar type of seal ring as the one shown in U.S. Pat. No. 6,086,069 is illustrated, for example, in FIG. 8. The seal ring 101 in FIG. 8 is, for example, mounted to a crawler unit 100.
In FIG. 8, 120 represents a shaft. The shaft 120 is disposed within a through bore of a roller 125, and a ring seal 101 is disposed in the chamber formed between the shaft 120 and the roller 125. The ring seal 101 provides a seal by preventing dusty water or muddy fluid from entering.
In this ring seal 101, a primary resilient ring 102 has an annularly shaped body whose cross section is “J”-shaped and outer surface forms a curved concave face 105. One end face of the primary resilient ring 102 is defined as outer fitting face 102A while the other end face is defined as inner fitting face 102B. Likewise, a secondary resilient ring 103 has also an annularly shaped body whose cross section is “J”-shaped and outer surface forms a curved concave face 105. Therefore one end face of the secondary resilient ring 103 defines outer fitting face 103A while the other end face defines inner fitting face 103B.
Next a first seal ring 110 has an annularly shaped body whose cross section is “U”-shaped and its radially extending end face of the first seal ring 110 defines a seal face 110A. An annular groove of the seal ring 110 which is located on the other side of the seal face 110A defines a mount groove portion 110B. Likewise, a second seal ring 111 has an annularly shaped body whose cross section is also “U”-shaped and its radially extending end face of the second seal ring 111 defines a mating seal face 111A. An annular groove disposed on the other side of the seal face 111A then defines a mount groove portion 111B.
The first resilient ring 102 and the second resilient ring 103 thus constructed as well as the first seal ring 110 and the second seal ring 111 are all installed within the chamber formed between the shaft 120 and the roller 125, as depicted in FIG. 8. Therefore the first resilient ring 102 and the second resilient ring 103 retain curved concave surfaces 105, 105 relative to an ambient passage chamber 126. Also the first resilient ring 102 and the second resilient ring 103 possess curved convex surfaces relative to a lubricant-filled internal chamber 127. The first resilient ring 102 exerts a resiliently urging force such that the seal surface 110A of the first seal ring 110 is pressed against the second seal ring 103. The opposed seal surfaces 110A and 111A being pressed against each other provide an effective seal for the process fluid coming into the ambient passage chamber 126.
In addition a floating seal device 150 shown in FIG. 9 is the second prior art related to the current invention. This floating seal device 150 include a first seal ring 152 and a second seal ring 153 which are disposed around the shaft in axially symmetric a manner. A seal surface 152A of the first seal ring 152 and a seal surface 153A of the second seal ring 153 therein exhibit a seal-tight joint. Such a joint between the seal surface 152A of the first seal ring 152 and the seal surface 153A of the second seal ring 153 is achieved by the resiliently urging forces due to compressed rubber materials as shown by the elliptic cross sections used for a first O-ring 155 and a second O-ring 156. For that purpose, the first O-ring 155 and the second O-ring 156 are disposed, respectively, between a housing and the first seal ring 152 and the housing and the second seal ring 153 such that the elliptic cross section forms an angle to the radial direction.
A first seal face 155A of the first O-ring 155 and a first seal face 156A of the second O-ring 156 individually form a sealing contact with the housing while a second seal face 155B of the first O-ring 155 and a second seal face 156B of the second O-ring 156, respectively, make a sealing contact with the first seal ring 152 and the second seal ring 153. However, the degree of the sealing contact at the seal surfaces 152A and 153A urged by the first O-ring 155 and the second O-ring 156 relies on the reaction force of the compressed rubber materials. Therefore a choice of hardness in rubber materials may vary and it makes difficult to make an optimal decision of rubber materials.
This floating seal device 150 provides a seal for a process fluid containing slurry. It can also be applied to a fluid containing fine particles. The first O-ring 155 and the second O-ring 156 which are resiliently compressed and disposed in a symmetric manner, respectively, provide urging forces to the first seal ring 152 and the second seal ring 153 so that a sealing contact is made between the opposed seal surfaces 152A and 153A. Therefore the fact that the elastic reaction forces due to the rubber materials of the first O-ring 155 and the second O-ring 156 is the source of the sealing contact at the seal surfaces 152A and 153A will lead to an acceleration of abrasion of the seal surfaces 152A and 153A caused by large urging forces.
In addition if slurry particles or as such are trapped at the joint surface between the first O-ring 155 and the first seal ring 152 or the second O-ring 156 and the second seal ring 153, the fine particles of slurry remain in the interface and cause the first O-ring 155 and the second O-ring 156 to be worn because of the resilient nature of the first O-ring 155 and the second O-ring 156. Furthermore a constant compressive stress given to the first O-ring 155 and the second O-ring 156 causes a stress relaxation and permanent deformation, which will reduce the intended resilient urging forces.
In the first prior art when a pressure accumulated in the ambient passage chamber 126 is applied to the first resilient ring 102 and the second resilient ring 103 where the pressure is received by the respective curved concave surfaces 105, 105, this will cause the curved concave surfaces 105, 105 to be further bent toward the internal chamber 127 which in turn will lessen the contact force at the seal surfaces 110A and 111A.
Promotion of the stress relaxation of the rubber material in the first resilient ring 102 and the second resilient ring 103 will lead to an unwanted permanent deformation in them. At the same time as the respective inner fitting faces 102B, 103B of the first resilient ring 102 and the second resilient ring 103, respectively, undergo elastic deformation in such a manner to depart from the mount groove portions 110B, 111B, the seal capability of the inner fitting faces 102B, 103B will deteriorate. As a consequence, fine particles contained in the process fluid or sediment located to the side of the ambient passage chamber 126 are trapped between the gaps between the inner fitting faces 102B, 103B and the mount groove portions 110B, 111B, respectively, which cause an abrasion of the inner fitting faces 102B, 103B and a decrease in their seal capability.
In the second prior art the first seal ring 152 and the second seal ring 153 are supported by the first O-ring 155 and the second O-ring 156, respectively. However, the urging force is originated from the resilient reaction force due to a small deformation in the compressed rubber materials of the first O-ring 155 and the second O-ring 156. Therefore the resilient urging force will quickly decrease as the rubber deformation gets small. For that reason the initial resilient urging force of the first O-ring 155 and the second O-ring 156 needs to be set relatively high by taking a subsequent stress relaxation into consideration. This, however, leads to the acceleration of abrasion of the seal surfaces 152A and 153A due to the high urging contact force.
Since the first seal ring 152 and the second seal ring 153 are exerted a resiliently urging force by the first O-ring 155 and the second O-ring 156 which are elastically deformed under compressive forces, a progress of the stress relaxation in the first O-ring 155 and the second O-ring 156 decreases their elasticity, as time proceeds, to provide a resiliently urging force to the seal surfaces 152A and 153A. Furthermore if slurry is introduced to the joint surface of the first O-ring 155 or the second O-ring 156, the slurry particles trapped at the joint surface of the first O-ring 155 or the second O-ring 156, respectively, cause an abrasion of the first O-ring 155 or the second O-ring 156.
The present invention is introduced to alleviate the above mentioned problems. A primary technical goal which this invention tries to achieve is to prevent the abrasion of seal surfaces even under the influence of a process fluid of high pressure or containing slurry. Another goal is to prevent the abrasion of seal surfaces attached with resilient seal rings and to improve the seal capability even when the seal surfaces are subjected to a muddy fluid or the like. Yet another goal is to prevent the stress relaxation of the resilient seal rings in conjunction with elastic deformation and to maintain the seal capability of the resilient seal rings.